A femme fatale (/ˌfɛm fəˈtæl, -ˈtɑːl/ FEM fə-TA(H)L, French: [fam fatal]; lit. 'fatal woman'), sometimes called a maneater, Mata Hari, or vamp, is a stock character of a mysterious, beautiful, and seductive woman whose charms ensnare her lovers, often leading them into compromising, deadly traps. She is an archetype of literature and art. Her ability to enchant, entice and hypnotize her victim with a spell was in the earliest stories seen as verging on supernatural; hence, the femme fatale today is still often described as having a power akin to an enchantress, seductress, witch, having power over men. Femmes fatales are typically villainous, or at least morally ambiguous, and always associated with a sense of mystification, and unease.

The term originates from the French phrase femme fatale, which means 'deadly woman' or 'lethal woman'. A femme fatale tries to achieve her hidden purpose by using feminine wiles such as beauty, charm, or sexual allure. In many cases, her attitude towards sexuality is lackadaisical, intriguing, or frivolous. In some cases, she uses lies or coercion rather than charm. She may also make use of some subduing weapon such as sleeping gas, a modern analog of magical powers in older tales. She may also be (or imply that she is) a victim, caught in a situation from which she cannot escape.

In early 20th-century American films, a femme fatale character was referred to as a vamp, a reference to The Vampire, Philip Burne-Jones's 1897 painting, and Rudyard Kipling's later 1897 poem, and the 1909 play and 1915 film A Fool There Was.

Female mobsters (including Italian-American Mafia or Russian Mafia) have been portrayed as femmes fatales in films noir. Femmes fatales are a recurring element in James Bond films.

The femme fatale archetype exists in the culture, folklore and myths of many cultures. Ancient mythical or legendary examples include Inanna, Lilith, Circe, Medea, Clytemnestra, Lesbia, Tamamo no Mae, and Visha Kanyas. Historical examples from classical times include Cleopatra and Messalina, as well as the biblical figures Delilah, Jezebel, and Salome. An example from Chinese literature and traditional history is Daji.

The femme fatale was a common figure in the European Middle Ages, often portraying the dangers of unbridled female sexuality. The pre-medieval inherited biblical figure of Eve offers an example, as does the wicked, seductive enchantress typified in Morgan le Fay. The Queen of the Night in Mozart's The Magic Flute shows her more muted presence during the Age of Enlightenment.

The femme fatale flourished in the Romantic period in the works of John Keats, notably "La Belle Dame sans Merci" and "Lamia". Along with them, there rose the gothic novel The Monk by Matthew Gregory Lewis, featuring Matilda, a very powerful femme fatale. This led to her appearing in the work of Edgar Allan Poe, and as the vampire, notably in Carmilla and Brides of Dracula. The Monk was greatly admired by the Marquis de Sade, for whom the femme fatale symbolised not evil, but all the best qualities of women; his novel Juliette is perhaps the earliest wherein the femme fatale triumphs. Pre-Raphaelite painters frequently used the classic personifications of the femme fatale as a subject.

In the Western culture of the late 19th and early 20th centuries, the femme fatale became a more fashionable trope, and she is found in the paintings of the artists Edvard Munch, Gustav Klimt, Franz von Stuck, and Gustave Moreau. The novel À rebours by Joris-Karl Huysmans includes these fevered imaginings about an image of Salome in a Moreau painting: